Electrical Contracting News (ECN) July 2017 | Page 37
FIRE DETECTION & SAFETY
in which the output meets the minimum
illumination requirement of 0.4 lumens/m 2
(lux) on a perpendicular surface.
To avoid having to install an
unacceptably large number of beacons,
manufacturers are typically designing to
meet smoke detector spacings. The result
is that W class devices are assessed in
terms of the dimensions of the cube of
light they cover and C devices are assessed
as the diameter of a cylinder of light. The
coverage of an O class device is a cuboid
of light, defined by the manufacturer
as independent of the EN54-23 height/
placement requirements.
A further important consideration
is that if the risk assessment does not
specify a VAD for a particular area, it
will still be acceptable to install a non-
compliant beacon as a supplementary
indicator to a sounder.
SPECIAL
FEATURE
‘The
development
of EN54-23
required a
fundamental
change in
visible alarm
technology.’
Red or white flash?
The fire industry has traditionally used a
red flash to denote an alarm condition.
This presented a challenge under EN54-
23, as the light intensity drops as it is
filtered through a red lens, requiring more
power to achieve the required coverage.
This loss can be as much as 80 per cent.
Installers and specifiers need to be aware
of this when selecting a VAD. If an existing
installation has VADs with red flash then
the colour of the flash has to remain the
same on any replacements or extensions to
the system.
Specifying
When selecting a beacon, room coverage,
flash colour and current consumption
are the key measures. The milliamp per
metre specification of a product offers a
good guide to selecting the most efficient
VAD possible.
The introduction of EN54-23 has led to
growth in the use of VADs and this is set to
continue. They offer the reassurance of a
visual indication to a fire alarm and help to
mitigate the risk to the building occupants.
Fully automated and highly reliable, used
as part of a comprehensive fire detection
system, VADs remove any human error
associated with systems that rely on human
interaction or the requirement to ensure
that portable tactile devices are working
and that the batteries are charged. The
standard enforces a specific illumination
level, ensuring that any visual alarm is
meaningful and inclusive to all.
The introduction of
EN54-23 has led to
growth in the use
of VADs.
METAL NAIL CLIPS AD - ECN_Layout 1 20/06/2017 11:29 Page 1
Meets the requirements of BS7671
3rd Amendment 7th Edition
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